Materials such as fabrics are characterized by a wide variety of functional and aesthetic characteristics. Of those characteristics, a particularly important feature is fabric surface feel or "hand." The significance of a favorable hand in a fabric is described and explained in U.S. Pat. Nos. 4,918,795 and 4,837,902, both to Dischler, the teachings of which are both entirely incorporated herein by reference.
Favorable hand characteristics of a fabric are usually obtained upon conditioning of prepared textiles (i.e., fabrics which have been de-sized, bleached, mercerized, and dried). Prior methods of prepared-fabric conditioning have included roughening of the finished product with textured rolls or pads. It has now been discovered, surprisingly, that such conditioning would favorably be performed while the target fabric is in its greige state or is unprepared. The conditioning of such fabrics provides heretofore unknown benefits in improvements in overall fabric strength, and the like (as discussed in greater detail below). Of great importance and necessity then within the textile treatment industry is a procedure through which greige or unfinished fabrics can be treated and subsequently finished which provides desirable hand to the target textile and does not adversely impact the ability for dyeing, decorating, and the like, the textile at a future point in time. Such processes have not been taught nor fairly suggested within the pertinent art. Thus, there is no prior teaching nor fair suggestion within the pertinent art which has accorded highly effective and easily duplicated textile hand improvements to greige goods and unfinished textiles.
In the textile industry, it is known to finish woven fabrics by abrading one or both surfaces of the fabric using sandpaper or a similarly abrasive material to cut and raise the fibers of the constituent yarns in the fabric. Through such a treatment, a resultant fabric is obtained generally exhibiting a closely raised nap producing a soft, smooth surface texture resembling suede leather. This operation, commonly referred to as sueding or sanding, is conventionally performed by a specialized fabric sueding machine wherein the fabric is passed under tension over one or more finishing rolls, covered with sandpaper or a similarly abrasive material, which are rotated at a differential speed relative to the moving fabric web. Such machines are described in U.S. Pat. Nos. 5,752,300 to Dischler, and 3,973,359 to Spencer, both hereby entirely incorporated by reference.
Another well known technique for enhancing aesthetic and performance characteristics of a fabric through the same type of surface-raising treatment is napping. Such a treatment provides a fabric exhibiting a softer hand, improved drapeability, greater fabric thickness, and better overall durability. Napping machinery generally utilizes rotatably driven cylinders including peripheral wire teeth, such as, normally, card clothing, over which the fabric travels under a certain amount of tension.
During a napping treatment the individual fibers are ideally pulled from the fabric body in contrast to sueding which ideally cuts the individual fibers. Sueding, however, presents some disadvantages including the fact that a certain amount of napping occurs simultaneously. Grit particles engage the surface fibers of the target fabric and inevitably pull them from the fabric body resulting in a relatively long pile. Such a long pile traps air at the surface of the fabric creating an insulating-type effect which thereby produces a warm feeling against the wearer's skin. Such an insulating effect is highly undesirable, particularly for apparel intended for summer wear. Upon utilization of strong synthetic fibers (i.e., nylon or polyester), this tendency for fibers to be pulled from the surface of the fabric is accentuated. More tension would thus be required to cut through such strong fibers (as compared to the force necessary to cut weaker ones) and the stronger fibers then are pulled more easily from the yarn. Upon engagement by an abrasive grit particle, sufficient tension to pull rather than easily cut the fibers is accorded. Pilling is thus more noticeable with strong synthetic fibers and where a long pile is created (and thus highly disadvantageous) because entanglement between adjacent fibers is more likely to occur, thereby resulting in highly objectionable and unwanted pills on the fabric surface.
Methods have been utilized in the past on prepared fabrics to produce a short pile in order to decrease the potential for pilling. These have included the use of sand paper with very fine grit, brush rolls with grit particles embedded in soft nylon bristles, and even blocks of pumice stone mounted upon oscillating bars. However, the fine grit sandpaper degrades easily and rapidly due to the loss of grit particles and the build-up of debris between the remaining particles Furthermore, the target fibers are not cut in this fashion as much as they are generally eroded. Thus, fine grit sandpaper does not provide an effective process of replacing the sueding techniques mentioned above. Soft nylon bristles also appear to merely erode the fibers away than cut and also is highly inefficient because of the light pressure such devices apply to the target fabric. Pumice stone, being very soft, is itself subject to damage in such operations and also facilitates unwanted build-up of fibrous debris within the treatment surface of the stone. Undesirable wet procedures are generally necessary to produce any effective sueding results for pumice stone and fine grit sandpaper treatments.
Another disadvantage of prior napping and/or sueding treatments concerns the situation where fill yarns are exposed on the surface of the target fabric. Being perpendicular to the action of the napping and/or sueding, such treatments tend to act primarily upon these exposed yarns rather than the warp yarns. Weaving economy generally dictates that the target fabric would be more heavily constructed in the warp direction and thus it would be highly advantageous for sueding to act primarily on such warp yarns since those yarns exhibit more strength to relinquish during the abrasion procedure.
As noted above, one of the most unpleasant and unsightly phenomena produced through the utilization of strong synthetic fibers within fabrics is pilling. This term is generally accepted to mean the formation of small balls of fiber which are created on the textile surface by the entanglement of free fiber ends. Such fibers which hold the pills to the base fabric do not break off because the synthetic fibers (such as polyester) exhibit a higher flex strength than natural fibers and thus small balls of twisted and entangled fiber cling to the fabric surface.
A number of procedures have been developed to counter this undesirable pilling effect within the textile industry. For instance, polyester fibers have been produced with low molecular weights or low solution viscosities in order to reduce the strength of the fibers resulting in fiber ends and nascent pills which more readily break off from the fabric surface (just as with natural fibers). However, such a reduction in strength (by about 40% from standard polyester fibers) leaves them highly susceptible to damage during further processing thus prohibiting processing on ring or rotor-spinning frames at the same speeds and with the same efficiencies as normal types of natural fibers (such as cotton). A further method to control pilling concerns the chemical weakening of fibers within woven fabrics. This is accomplished through the application of super-heated steam or aqueous solutions of acids, ammonia, ammonia vapors, or amines. In such an instance, however, the entire fabric strength is sacrificed with no concomitant enhancement of hand. Furthermore, the potential for fabric defects (such as stains and uneven dyeing) is increased. An additional method is to utilize yarns having high twist. However, such resultant fabrics exhibit a harsh hand and the internal compression generated by the twist of the individual fibers makes it very difficult to properly de-size, mercerize, and dye fabrics comprising such high-twist yarns. It would thus be highly desirable to obtain substantial reduction in pilling for fabrics comprising strong synthetic fibers without recourse to the above processes and methods. Unfortunately, the prior art has not accorded such an improvement with a simultaneous improvement in hand of the fabric.
The present invention provides a hand improvement method to unfinished fabrics in a manner not disclosed in the known prior art. Such a method also substantially eliminates pilling; in fabrics comprised of synthetic fibers simultaneously while providing the aforementioned improvements of the hand of the target fabric.